[Y/Mg] vs. stellar age dependence. Top panel: 342 stars with σ_YII <  0.2 and σ_MgI <  0.1 dex; middle panel: 123 turn-off stars with σ_YII <  0.1 dex and σ_MgI <  0.05 dex; bottom panel: 22 turn-off thin disc stars with σ_YII <  0.05 dex and σ_MgI <  0.05 dex. The symbols are as in Fig. 6, and are also colour-coded for the stellar metallicity. The dotted line shows the (Nissen 2015) fit for solar type stars (here c = 0.1 dex); the red solid line (bottom panel) is the fit for the high-precision sample of thin disc stars.